Aiming at a reduced manufacturing cost and a lowered price of a panel, the design of a data driving unit (source IC) has been widely used in large-sized panels.
FIG. 1 schematically shows a structural diagram of an array substrate of a thin-film transistor liquid crystal display. With reference to FIG. 1, a total quantity of 2n data lines of the display is shown, and the data lines are successively numbered from one side to the other side in the drawing. Reference signs X(1), X(2), . . . , X(n−1), X(n) . . . , X(2n−1) and X(2n) indicate 2n data lines of the liquid crystal display respectively.
FIG. 1 further shows a structural schematic diagram of a panel with a data driving unit (source IC) in the prior art. With reference to FIG. 1, for a large-sized panel, the impedance difference between the central data line on the panel close to the data driving unit (source IC) and two end data lines on the panel away from the data driving unit (source IC) is relatively large.
FIG. 2 schematically shows data line impedance under an ideal condition, wherein the horizontal coordinate indicates the numbers of the data lines, while the vertical coordinate indicate the impedance values of the data lines designated with different numbers. In FIG. 2, R0 schematically indicates an ideal impedance, i.e. a reference value for impedance compensation, with the black solid line schematically illustrating the impedance values of the data lines of different numbers under the ideal condition, and RI schematically indicates the minimum impedance value of the data lines under the ideal condition. It could be seen that under the ideal condition, the impedance values of the data lines constitute a decreasing arithmetic progression from data line X(1) to data line X(n), and an increasing arithmetic progression from data line X(n+1) to data line X(2n), respectively. The impedance values corresponding to data lines X(n) and X(n+1) are minimum, and thus form the minimum impedance value R1 for the data lines.
FIG. 3 schematically shows compensation impedances under the ideal condition, wherein the horizontal coordinate indicates the numbers of data lines, and the longitudinal coordinate indicates impedance compensation values. As shown in FIG. 3, for the purpose of compensating unequal impedances of the data lines due to different positions, fixed impedance compensation may be performed in the data driving unit (source IC) on the basis of the impedance differences between different data lines. The black solid line schematically illustrates the impedance compensation values of the data lines designated with different numbers under the ideal condition. It could be seen from FIG. 3 that under the ideal condition, the impedance compensation values of the data lines constitute an increasing arithmetic progression from data line X(1) to data line X(n), and a decreasing arithmetic progression from data line X(n+1) to data line X(2n), respectively. The impedance compensation values corresponding to the data lines X(n) and X(n+1) are maximum, which equal the value of R0-R1 as shown in FIG. 2, namely, the difference between the ideal impedance value and the minimum impedance value of the data lines.
FIG. 4 shows a total load impedance of a data driving unit under the ideal condition. It could be seen that the function curve of the total load impedance shows a straight line under the ideal condition, which means that total load impedance values corresponding to all the data lines are equal with the ideal impedance value R0.
However, FIG. 2, FIG. 3 and FIG. 4 are merely directed to the results of impedance compensation technical solutions under the ideal condition in the prior art. Now the practical results of impedance compensation for data lines will be introduced below in conjunction with FIG. 5, FIG. 6 and FIG. 7.
In practical situations, due to the limitation of process conditions, the actual impedance profile of the data lines of the liquid crystal panel is not in accordance with the curve shown in FIG. 2, but is rather similar to the one shown in FIG. 5. The horizontal coordinate in FIG. 5 indicates the numbers of different data lines, and the solid line in FIG. 5 illustrates the impedances of different data lines under practical conditions. With comparison to FIG. 2, it could be seen that the impedance profile of the data lines under practical conditions cannot form an arithmetic progression between the minimum impedance R1 and the reference impedance value R0, but exhibits certain irregular fluctuations.
FIG. 6 shows a compensation impedance profile in the prior art. The curve shown in FIG. 6 is consistent with the one shown in FIG. 3, which means that in the prior art, the compensation solution under the ideal condition is even adopted for practical conditions. With reference to FIG. 6, the black solid line illustrates impedance compensation values for data lines designated with different numbers in the prior art. In other words, with the compensation solution for data lines in the prior art, the impedance compensation values for data lines form an increasing arithmetic progression from data line X(1) to data line X(n), and a decreasing arithmetic progression from data line X(n+1) to data line X(2n), respectively. The impedance compensation values corresponding to data lines X(n) and X(n+1) are maximum, which equal R0-R1 from FIG. 5, namely the difference between the ideal impedance value and the minimum impedance value of the data lines.
However, the actual impedance profile of the data lines as shown in FIG. 5 deviates with irregular fluctuations from the impedance profile of the data lines under the ideal condition as shown in FIG. 2 due to practical processing conditions, and as a result of which, the actual compensated total load impedance by means of the compensation solution in the prior art is in accordance with the one shown in FIG. 7. The black solid line in FIG. 7 schematically illustrates a total load impedance of a data driving unit in the prior art. With reference to FIG. 7, it could be seen that under practical conditions, the fluctuation caused by the process conditions can not be improved, and the curve in FIG. 7 cannot be in accordance with the ideal image of FIG. 4. When the fluctuation amplitude of the process conditions reaches a certain degree, the display effect would be negatively affected, and certain display defects, such as vertical black and white strips, color shift, and the like, would be generated.